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Home > A-Series EFI / Injection > Everything powers up except Main Relay


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Member #: 11680
Junior Member

2000 MPI Mini with Microsquirt V2.2

There's no power to the ECU with key switch on or crank. Immobilizer seems OK as it cranks when the light is off. If I manually close the Main Relay everything works, power to the ECU, FP on for 3 seconds, ECU communicates, etc. If I manually ground the white/pink wire the Main relay is powered. ECU pin 22 (Black)(Main Relay Control) is wired to a daughter board containing two BIP373's, connected to the right side terminal of one of the BIPs. Is this the proper way to control the main relay? I thought the BIPs were supposed to drive the ignition system. Where should the Black ECU connector pin 22 wire be connected to on the microsquirt board in order to ground the main relay on key switch on?

Rod S

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5840 Posts
Member #: 2024
Formally Retired

Rural Suffolk

Going back to your original post (Dec 2017) and its photo, it's actually a microsquirt module that someone has mounted in the original Rover MEMS ECU case ???

So first, when you refer to pin numbers, do you mean the pin number on the original Rover connector(s) (red or black) or the microsquirt module board ???

A pair of BIPs on a separate board is to be expected, for the ignition as you say, as the module itself doesn't have high voltage ignitors (some of the cased microsquirts do, but not the module) and they do have to be wired in a specific way with regard to the main relay and fuel pump relays to ensure everything is powered up in the correct order.

But we'll need a bit more detail.
Pin 22 for example on the microsquirt module is the fuel pump relay output, but what it is on the MEMS plug(s) I haven't a clue without searching out my Rover wiring diagrams CD. Equally, is the white/pink the original loom wire or new wiring inside the case ?

However, from the sequence of events you describe when you manually force the main relay to operate, it may well be an issue with the original wiring or if any bits of the original wiring were altered (by whoever installed this) in a way that doesn't actually suit the module.

In a stand-alone megasquirt install (ie, a car which didn't previously have EFI) a new main relay would usually be operated by the ignition switch alone, and then the fuel pump relay (and other things like actual ignition) would be controlled by the ECU but without any notes, wiring diagrams, etc. it's hard to second guess how someone else chose to use the existing relays.

EDIT - just one further thought - you say the immobilizer seems OK but I thought that on the later MEMS units part of the immobilizer function was within the ECU itself. I'll dig the factory wiring diagrams out later but if my memory is correct, whoever wired this in must have (or should have) done something to get around it.

Edited by Rod S on 10th Jan, 2018.

Schrödinger's cat - so which one am I ???

Home > A-Series EFI / Injection > Everything powers up except Main Relay
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